1. Field of the Invention
The present invention relates to a wheel suspension system for automobiles, and particularly to an improvement in a wheel suspension system which comprises a pair of upper and lower control arms connected at their leading ends to a knuckle which carries a wheel, each of the base ends of the arms being vertically swingably pivoted respectively at front and rear spaced positions to a vehicle body.
2. Description of the Prior Art
Such wheel suspension systems are well known as a double wishbone type (for example, see Japanese Patent Publication No. 28123/69).
In such conventional wheel suspension system, the upper and lower control arms are pivoted at their base ends respectively through elastic members to horizontal shafts fixedly mounted on a vehicle body. Therefore, the longitudinal compliance and caster rigidity during braking are governed by spring constants of these elastic members.
In general, in order to prevent shocks from being transmitted to the vehicle body to the utmost, such as shocks generated when a wheel gets over a protrusion on a road surface, it is necessary to provide the wheel suspension system with a large longitudinal compliance. And in order to assure a straight advancing property of a wheel during braking, it is necessary to give a large caster rigidity to the wheel suspension system.
In the conventional wheel suspension system, however, if the spring constant of an elastic member is set at a smaller value for providing a larger longitudinal compliance, the caster rigidity is reduced to degrade the straight advancing property of the wheel. On the contrary, if the spring constant of the elastic member is set at a larger value to provide a larger caster rigidity during braking, the longitudinal compliance is reduced, accompanied by an adverse deterioration of the riding comfort. Consequently, it is difficult to satisfy both of the longitudinal compliance and the caster rigidity during braking.